Quality Evaluation of Gentamicin Sulfate Reference Standards in Japanese Pharmacopoeia Using Hydrophilic Interaction Chromatography Combined With Tandem Mass Spectrometry.

BACKGROUND: Through the recent development of analytical technology, antibiotics quantification in the Japanese Pharmacopoeia (JP) has changed from traditional microbiological assays to physicochemical methods with high specificity and precision. However, for several multicomponent antibiotics without typical UV absorption, potency cannot be directly determined using instrumental methods such as high-performance liquid chromatography; therefore, traditional microbiological assays are still used. Gentamicin sulfate (GmS), which consists of three major components, C1, C1a, and C2, is such a typical antibiotic, and its antimicrobial potency continues to be assayed using microbiological methods in JP monographs. Introduction of a physicochemical assay for GmS is needed to help ensure its quality and quantity. OBJECTIVE: This study aimed to develop quality control measures for GmS that could be complementary to quantitative assays and purity tests specified in the JP. METHODS: For each gentamicin C component (C1, C2, and C1a), theoretical potencies were determined based on the quantitative relationship between purity and potency, as measured by quantitative 1H NMR and microbiological assays, respectively. Two lots of the JP reference standard (RS) were used as test samples, with the contents of each component and impurity (sisomicin and garamine) being determined using hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS). RESULTS: The ratios of theoretical potency for C1, C2, and C1a were 1.00, 1.21, and 1.80, respectively. The potencies of the GmS JP RSs, which were estimated based on the contents and theoretical potency of each C component, corresponded well with those determined through microbiological assays. Marked differences in impurities (%) between the two RS lots were highlighted by quantifying sisomicin and garamine. CONCLUSIONS: The developed analytical procedure enabled the characterization of two different JP RSs in terms of content ratio, potencies, and impurities. HIGHLIGHTS: Novel analytical procedures useful for routine quality control of GmS were developed using HILIC-MS/MS.

[Identification Methods for Pseudo-crystalline Polymorphs of Thiamine Chloride Hydrochloride, Which Transform Easily Depending on the Handling Environment].

Three forms of pseudo-crystalline polymorph of thiamine chloride hydrochloride are dependent on hydration states. We investigated how the measurement environment affects the transition of the pseudo-crystalline polymorph, and aimed to establish a reliable method of identifying the forms clearly by IR spectrophotometry. We prepared three pseudo-crystalline forms and compared their IR spectra. In the IR spectra obtained by the potassium chloride (KCl) disk method, Form II was identified based on its characteristic absorption, but Forms I and III could not be distinguished clearly. Form I transformed to Form III after mixing with undried KCl powder, and Form III transformed to Form I by simply being left in the laboratory environment. These results suggested that the reversible transformation between Forms I and III occurred depending on the hydration status during the process of measurement, as measured by the shift in the absorption wavenumber of the primary alcohol stretching vibration. In addition, Forms I and III could not be distinguished clearly by the X-ray powder diffraction and their crystalline forms were similar plate crystals. However, in the IR spectra by the attenuated total reflection (ATR) method, the three forms could be identified based on each characteristic absorption. In summary, the ATR method does not require pretreatment for sample analysis, can be performed quickly, and is thus suitable to identify crystalline polymorph forms such as pseudo-crystalline polymorphs of thiamine chloride hydrochloride, which transform easily depending on the hydration status in a measurement environment.

The ubiquinone synthesis pathway is a promising drug target for Chagas disease.

Chagas disease is caused by infection with the protozoan parasite Trypanosoma cruzi (T. cruzi). It was originally a Latin American endemic health problem, but now is expanding worldwide as a result of increasing migration. The currently available drugs for Chagas disease, benznidazole and nifurtimox, provoke severe adverse effects, and thus the development of new drugs is urgently required. Ubiquinone (UQ) is essential for respiratory chain and redox balance in trypanosomatid protozoans, therefore we aimed to provide evidence that inhibitors of the UQ biosynthesis have trypanocidal activities. In this study, inhibitors of the human COQ7, a key enzyme of the UQ synthesis, were tested for their trypanocidal activities because they were expected to cross-react and inhibit trypanosomal COQ7 due to their genetic homology. We show the trypanocidal activity of a newly found human COQ7 inhibitor, an oxazinoquinoline derivative. The structurally similar compounds were selected from the commercially available compounds by 2D and 3D ligand-based similarity searches. Among 38 compounds selected, 12 compounds with the oxazinoquinoline structure inhibited significantly the growth of epimastigotes of T. cruzi. The most effective 3 compounds also showed the significant antitrypanosomal activity against the mammalian stage of T. cruzi at lower concentrations than benznidazole, a commonly used drug today. We found that epimastigotes treated with the inhibitor contained reduced levels of UQ9. Further, the growth of epimastigotes treated with the inhibitors was partially rescued by UQ10 supplementation to the culture medium. These results suggest that the antitrypanosomal mechanism of the oxazinoquinoline derivatives results from inhibition of the trypanosomal UQ synthesis leading to a shortage of the UQ pool. Our data indicate that the UQ synthesis pathway of T. cruzi is a promising drug target for Chagas disease.

Identification of small molecule inhibitors of human COQ7.

Given that the associated clinical manifestations of ubiquinone (UQ, or coenzyme Q) deficiency diseases are highly heterogeneous and complicated, effective new research tools for UQ homeostasis studies are awaited. We set out to develop human COQ7 inhibitors that interfere with UQ synthesis. Systematic structure-activity relationship development starting from a screening hit compound led to the identification of highly potent COQ7 inhibitors that did not disturb physiological cell growth of human normal culture cells. These new COQ7 inhibitors may serve as useful tools for studying the balance between UQ supplementation pathways: de novo UQ synthesis and extracellular UQ uptake.

Survey of peptide quantification methods and comparison of their reproducibility: A case study using oxytocin.

USP's peptide reference standards content is typically determined using an HPLC assay against an external standard for which the purity was determined by a mass balance approach. To explore the use of other analytical methods, the USP Biologics Department conducted a multi-laboratory collaborative study. The study determined the inter-laboratory variability for peptide quantitation using the following methods: HPLC assay, quantitative nuclear magnetic resonance (qNMR) spectroscopy, or amino acid analysis (AAA). The three methods were compared with regard to their suitability for quantitation of the nonapeptide oxytocin. In this study, the HPLC assay method using the same peptide bulk material as the standard showed the lowest inter-lab variability. The coefficient of variation (%CV) was calculated without counting the uncertainty associated with the purity assignment of the standard with mass balance. The proton qNMR method is a direct measurement of the peptide against an internal standard, which is not difficult to perform under common laboratory conditions. Because of the simpler operation and shorter analytical time, qNMR as a primary method for peptide reference standard value assignment deserves further exploration.

Characterization of crystal water molecules in a high-affinity inhibitor and hematopoietic prostaglandin D synthase complex by interaction energy studies.

Hematopoietic prostaglandin D synthase (H-PGDS) is one of the two enzymes that catalyze prostaglandin D2 synthesis and a potential therapeutic target of allergic and inflammatory responses. To reveal key molecular interactions between a high-affinity ligand and H-PGDS, we designed and synthesized a potent new inhibitor (KD: 0.14 nM), determined the crystal structure in complex with human H-PGDS, and quantitatively analyzed the ligand-protein interactions by the fragment molecular orbital calculation method. In the cavity, 10 water molecules were identified, and the interaction energy calculation indicated their stable binding to the surface amino acids in the cavity. Among them, 6 water molecules locating from the deep inner cavity to the peripheral part of the cavity contributed directly to the ligand binding by forming hydrogen bonding interactions. Arg12, Gly13, Gln36, Asp96, Trp104, Lys112 and an essential co-factor glutathione also had strong interactions with the ligand. A strong repulsive interaction between Leu199 and the ligand was canceled out by forming a hydrogen bonding network with the adjacent conserved water molecule. Our quantitative studies including crystal water molecules explained that compounds with an elongated backbone structure to fit from the deep inner cavity to the peripheral part of the cavity would have strong affinity to human H-PGDS.

The establishment and validation of efficient assays for anti-IIa and anti-Xa activities of heparin sodium and heparin calcium.

Heparin is used as an anticoagulant drug. The anticoagulation process is mainly caused by the interaction of heparin with antithrombin followed by inhibition of anticoagulant factor IIa and factor Xa. The anti-factor IIa and anti-factor Xa activities of heparin are critical for its anticoagulant effect; however, physicochemical methods that can reflect these activities have not been established. Thus, the measurements of anti-IIa and anti-Xa activities by biological assay are critical for the quality control of heparin products. Currently in the Japanese Pharmacopoeia (JP), the activities of heparin sodium and heparin calcium are measured by an anti-Xa activity assay (anti-Xa assay), but anti-IIa activity is not measured. Here, we established an anti-IIa activity assay (anti-IIa assay) and an anti-Xa assay having good accuracy and precision. When samples having a relative activity of 0.8, 1.0 and 1.2 were measured by the established anti-IIa and anti-Xa assays in nine laboratories, good accuracy (100.0-102.8% and 101.6-102.8%, respectively), good intermediate precision (1.9-2.1% and 2.4-4.2%, respectively) and good reproducibility (4.0-4.8% and 3.6-6.4%, respectively) were obtained. The established anti-IIa and anti-Xa assays have similar protocols, and could be performed by a single person without a special machine. The established assays would be useful for quality control of heparin.

A fluorescent-based high-throughput screening assay for small molecules that inhibit the interaction of MdmX with p53.

A fluorescent-based high-throughput screening (HTS) assay for small molecules that inhibit the interaction of MdmX with p53 was developed and applied to identify new inhibitors. The assay evaluated the MdmX-p53 interaction by detecting the quenching of the fluorescence of green fluorescent protein (GFP) fused to the MdmX protein, after its interaction with a p53 peptide labeled with a fluorescence quencher. In this report, the developed HTS assay was applied to about 40 000 compounds, and 255 hit compounds that abrogated the GFP quenching were selected. Next, the obtained hits were reevaluated by other assays. First, their effects on the diffusion time of a fluorescently-labeled p53 peptide after incubation with the MdmX protein were tested by measuring the diffusion time using fluorescence correlation spectroscopy, and six stable hit compounds with IC(50) values less than 5 µM were selected. Next, we further confirmed their inhibition of the MdmX-p53 interaction by surface plasmon resonance. To indicate the efficacy of the hit compound as a candidate anticancer drug, we showed that the hit compound triggered apoptosis after p53 and p21 accumulation in cultured MV4;11 leukemia cells. Thus, the new HTS assay is effective for obtaining novel MdmX-p53 interaction inhibitors that are valuable as candidate compounds for cancer treatment.

Population divergence of the sentinel crab Macrophthalmus banzai is consistent with regional breeding season differences.

We compared the breeding season and genetic population structure of six sentinel crab (Macrophthalmus banzai) populations in southwestern Japan. Ovigerous females from Northern group populations (Wakayama, Kochi, and Tanega-shima) were observed from March to September, whereas ovigerous females from Southern group populations (Amami-oshima, Okinawa-jima, and Iriomote-jima) were observed from October to May. Genetic analysis using two markers corresponding to mitochondrial DNA encoding cytochrome oxidase subunit I (COI) and the large subunit of ribosomal RNA (16Sr-RNA) revealed a marked genetic difference between the Northern and Southern groups. A genetic boundary exists between the Tanega-shima and Amami-oshima populations, which is consistent with the interpopulation difference in the breeding season.

A novel Pim-1 kinase inhibitor targeting residues that bind the substrate peptide.

A new screening method using fluorescent correlation spectroscopy was developed to select kinase inhibitors that competitively inhibit the binding of a fluorescently labeled substrate peptide. Using the method, among approximately 700 candidate compounds selected by virtual screening, we identified a novel Pim-1 kinase inhibitor targeting its peptide binding residues. X-ray crystal analysis of the complex structure of Pim-1 with the inhibitor indicated that the inhibitor actually binds to the ATP-binding site and also forms direct interactions with residues (Asp128 and Glu171) that bind the substrate peptide. These interactions, which cause small side-chain movements, seem to affect the binding ability of the fluorescently labeled substrate. The compound inhibited Pim-1 kinase in vitro, with an IC(50) value of 150 nM. Treatment of cultured leukemia cells with the compound reduced the amount of p21 and increased the amount of p27, due to Pim-1 inhibition, and then triggered apoptosis after cell-cycle arrest at the G(1)/S phase. This screening method may be widely applicable for the identification of various new Pim-1 kinase inhibitors targeting the residues that bind the substrate peptide.

Staphylococcal peptidoglycan suppresses production of interleukin-2 by T cells through a T cell-derived factor induced by direct contact between T cells and monocytes.

During the last 2 decades, the incidence of sepsis due to gram-positive bacteria has increased dramatically. Nevertheless, effects of the cell-wall components that do not contain endotoxin, on immunity, are still largely unknown. Here, we demonstrate, for the first time, that the gram-positive bacterial cell-wall component peptidoglycan (PGN) severely inhibits the production of interleukin (IL)-2 by cultured human peripheral blood mononuclear cells stimulated with anti-CD3 and anti-CD28 antibodies. Furthermore, we provide evidence that the inhibitory effect is mediated predominantly by a soluble mediator produced by T cells and that the production of the inhibitory mediator is induced by direct cell-to-cell contact of T cells with PGN-stimulated monocytes. The T cell-derived inhibitory mediator is distinct from known immunosuppressive lymphokines, such as IL-10 and IL-4. In light of the key role of IL-2 in cell-mediated immunity, it can be suggested that PGN induces the dysfunction of cell-mediated immunity.

Suppression by Candida albicans beta-glucan of cytokine release from activated human monocytes and from T cells in the presence of monocytes.

The effect of a soluble beta-glucan from Candida albicans (CSBG) on cytokine production by cultured human peripheral blood mononuclear cells (PBMC) was assessed. CSBG induced a slight increase in the spontaneous release of proinflammatory cytokines, such as interleukin (IL)-6, but significantly suppressed endotoxin-induced IL-6 production in cultures of PBMC and monocytes isolated from PBMC. CSBG also suppressed the release of type 1 cytokines, IL-2, and interferon-gamma. These findings suggest that CSBG suppresses monocyte functions directly and thus suppresses T cell function indirectly. CSBG may play a role in the development of candidiasis.

Evaluation of the in vitro pyrogen test system based on proinflammatory cytokine release from human monocytes: comparison with a human whole blood culture test system and with the rabbit pyrogen test.

The reliability of an in vitro pyrogen test system based on proinflammatory cytokine release from human monocytic cells was assessed by comparison with a test system based on a human whole blood culture as well as with the conventional rabbit pyrogen test. The human cells used as the pyrogen indicator cells were newly selected by subcloning of a human monocytic cell line, Mono-Mac-6. The selected cells, named MM6-CA8, responded to various pyrogens, including endotoxin, peptidoglycan (PG), Staphylococcus aureus Cowan 1 (SAC), and poly(I x C), with a high sensitivity and produced proinflammatory cytokines, such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor alpha. Among these cytokines, IL-6 was produced most sensitively in response to traces of the pyrogens and detected in the largest quantities in the culture medium. The cytokine-producing responses of MM6-CA8 cells correlated significantly with the responses of cultured human whole blood, which represents an ex vivo culture test system reproducing pyrogen-induced cytokine production in the human body. In terms of cytokine inducibility, the pyrogens were ranked in the order endotoxin > PG > poly (I. C) > SAC in both culture systems, a ranking which almost agreed with the ranking of their pyrogenicity as assessed by the rabbit pyrogen test. These results suggest that the in vitro responsiveness of MM6-CA8 cells to various pyrogens is highly relevant for human pyrogenic reactions. Therefore, the in vitro test system is useful and reliable for detecting the presence of materials that are pyrogenic for humans.

[The Endotoxin 10000 Reference Standard of the National Institute of Health Sciences (the Japanese Pharmacopoeia Endotoxin 10000 Reference Standard) (Control 0211)].

To establish the fifth lot (Control 0211) of the Endotoxin 10000 Reference Standard of the National Institute of Health Sciences (the Japanese Pharmacopoeia Endotoxin 10000 Reference Standard), a candidate standard (CS) was prepared and then evaluated. The potency of the CS was assayed against USP Endotoxin Reference Standard (Lot G-1) and defined a s containing approximately 16,000 endotoxin units (EU) per vial by a collaborative study in which 5 laboratories participated. Based on the results, the CS was authorized to be the fifth lot of the Endotoxin 10000 Reference Standard containing 16,000 EU per vial.

[The Endotoxin 100 Reference Standard of the National Institute of Health Sciences (the Japanese Pharmacopoeia Endotoxin 100 Reference Standard) (Control 0201)].

To establish the third lot (Control 0201) of the Endotoxin 100 Reference Standard of the National Institute of Health Sciences (the Japanese Pharmacopoeia Endotoxin 100 Reference Standard), a candidate standard (CS) was prepared and then evaluated. The potency of the CS was assayed against USP Endotoxin Reference Standard (Lot G-1) and defined as containing approximately 130 endotoxin units (EU) per vial by a collaborative study in which 5 laboratories participated. Based on the results, the CS was authorized to be the third lot of the Endotoxin 100 Reference Standard containing 130 EU of endotoxin per vial.